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Urban Food Garden

VEGETABLE CROP ROTATION

Crop rotation is the practice of rotating where crops are grown in a sequential pattern so that crops of a given type are not grown in the same place twice  in a row.  This webpage explains the four crop and the key crop rotation methods.

Advantages of vegetable crop rotation

There are a number of reasons why it is a good idea to practice vegetable crop rotation.  They are:-

  • To prevent the build-up of pests and pathogens that can occur when vegetables of a specific family group are grown continuously in the same area.
  • To enrich the soil with bacteria, fungi and protozoa. Different varieties of which thrive depending on the type of vegetables that have been planted.
  • To reduce the depletion of trace elements. Some vegetables draw disproportionate amounts of specific trace elements, if the same vegetables are continually grown in the same bed this can lead to a shortage of the elements they use.

For these reasons your vegetable garden will be healthier and more productive if you practice crop rotation. There are any number of different crop rotation plans to choose from but for simplicity I will look at just two, the four step crop and key crop rotation plans.  Though I do briefly refer to some other options.

The four step crop rotation plan

Plant each of the four vegetable groups in four separate beds and rotate them in order of what comes next as shown in the diagram below.  By following this plan you will ensure that each vegetable group will only be planted in each bed once every four years.

Four step crop rotation plan planting order

To maximise the benefits of crop rotation it is important that they be planted in the above order.

Vegetable groups for the four step crop rotation plan

Key vegetables in each of the four crop rotation groups

The problems with crop rotation plans

While crop rotation looks simple on paper there are several factors that can make putting a crop rotation plan into practise quite difficult at times.  

  • Crop rotation plans assume that you use equal space to grow the different groups of vegetables but usually the spacing required is much more uneven.
  • Gardeners rarely have vegetable beds of equal size and shape, which can cause space issues when rotating crops.
  • Vegetable growing times to harvest vary enormously. For example rocket takes as little as six weeks to harvest time while the growing season for tomatoes is several months.
  • Some companion planting practices contradict crop rotation practices.
the key crop rotation

For the above reasons I prefer to practice what I call Key Crop rotation.  Which is rotating the key crops and planting the other crops in the gaps in between and around the key crops.  Key crops are the ones that you grow the most of and take up the most space.  My key crops are tomatoes, corn, silverbeet, brassicas and carrots/beetroot, though these key crops will vary depending on the individual gardener’s tastes.

Key crop rotation is not perfect, the plantings are less likely to be in the proper sequential order and sometimes the lesser vegetables end up being grown in the same space they were in last time.  But I have found key crop rotation easier to manage than traditional crop rotation practices.

Other crop rotation plans

Two other common crop rotation plans are:-

  • THREE CROP ROTATION
    Involves reorganising the vegetable varieties into three simplified groups.
         1. ROOT AND BULB
         2. FRUIT AND SEEDS
         3. LEAF AND STEM
    This  simpler crop rotation plan is best suited to small gardens with limited space.
  • FIVE CROP ROTATION PLAN
    Includes a fifth group which is left fallow or sown with a manure crop.  This works best in larger gardens where there is plenty of spare land.
Recording crop plantings

Whatever type of crop rotation plan you use it will be easier to implement if you record what beds the different vegetables were planted in each season.  This can be as simple as recording your plantings in a notebook (as I used to do) or something more elaborate like a spread sheet.

These days I record my vegetable plantings using an excel spread sheet.

Crop rotation exemptions

It is possible to plant some vegetables repeatedly in the same spot year after year but the longer you do it the more likely you are to end up with disease problems.
I have planted my potatoes in the same spot for over fifteen years now, planting in mid-spring then fallowing the bed after the crop has been harvested in early winter.  I do this because potatoes are hard to remove from a bed once planted and the bed they are planted in gets no sun in the winter, so not much can be planted in it then.

TOP: My potato bed in summer.  BOTTOM: The same bed fallowed in winter.

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